Olefin oligomerization process and catalyst

ABSTRACT

A process for oligomerization of a lower olefin having 2 to 8 carbon atoms which comprises contacting said lower olefin with a catalyst composition comprising a transition metal complex selected from complexes of nickel and palladium with a fluoro-organic thiol or sulfide ligand, having a single sulfur atom in a ligating position and wherein the carbon atom adjacent the carbon to which the sulfur atom is attached has at least one fluoro substituent and with the proviso that said fluoro-organic thiol or sulfide does not contain any other ligating group or atom in a ligating position which will displace fluoro as a ligand, and an organometallic-reducing agent selected from the group of borohydride and organoaluminum halides and alkoxides.

BACKGROUND OF THE INVENTION

This invention relates to an improved olefin oligomerization process andcatalyst for preparing C₆ -C₃₀ olefin products. In another aspect, theinvention relates to a method for preparing said catalyst.

Olefin oligomers are used for a variety of industrial products and havebeen produced by a variety of catalytic processes. For example, U.S.Pat. No. 3,424,815 describes the preparation of alpha-olefin oligomersusing a catalyst comprising the product of certain nickel chelates witha halide-free organoaluminum compound such as alkyl aluminum alkoxides.Patentee teaches that the nickel chelating ligand-anion is substitutedwith electron withdrawing groups, i.e., nitro, halo, cyano orcarboalkoxy and that superior results are obtained when the chelatingligands are halogenated organic ligands.

U.S. Pat. No. 3,592,870 discloses olefin dimerization catalysts formedfrom an organoaluminum compound and one of the following nickelcomplexes: (a) bis(beta-mercaptoethylamine)nickel (II) complex; (b)alpha-diketobis(beta-mercaptoethylimine)nickel (II) complex; (c)S,S-disubstituted bis(beta-mercaptoethylamine) nickel (II) complex; or(d) S,S-disubstituted-alpha-diketone bis(beta-mercaptoethylimine)nickel(II) complex. Under (c) and (d) are included complexes of the formulas:##STR1## wherein X is halide and R¹ and R² are certain enumeratedorganic radicals and R³ is as defined for R² or hydrogen.

U.S. Pat. No. 4,069,273 describes a process for dimerizing low molecularweight linear alpha-olefins using a complex ofbis(1,5-cyclooctadiene)nickel and hexafluoro-2,4-pentanedione as thecatalyst. Patentee describes his process as producing a highly linearolefin product. U.S. Pat. No. 4,366,087 describes a process foroligomerizing olefins using a catalyst containing a nickel compoundhaving the formula (R₁ COO)(R₂ COO)Ni, wherein R₁ is a hydrocarbylradical having at least 5 carbon atoms and R₂ is a haloalkyl radical andan organic aluminum halide. As can be seen from the examples in thispatent, patentee's process afforded a product containing a large amountof branched olefins. A number of catalyst systems used for thepolymerization of olefins are described in Chemical Review 86 (1986) pp.353-399.

One of the principal uses of C₆ -C₃₀ olefins is as intermediates fordetergents, e.g., sulfonated alkyl benzenes. When used for this purpose,the C₆ -C₃₀ olefin product should have a high proportion of linearolefins because detergents produced from linear olefins are generallymore readily biodegraded than those produced with branched olefins.Similarly, mono-branched olefins are generally more readily biodegradedthan multibranched olefins and accordingly, more desirable fordetergents.

SUMMARY OF THE INVENTION

The present invention provides an oligomerization process and catalystwhich produces excellent yields of olefin oligomers having a highproportion of linear olefins, typically on the order of 80% by weight ormore and a combination of linear olefins plus mono-branched olefinscontent on the order of 90% by weight or more. Thus, the present processis especially applicable for the production of olefins for detergents orother surfactants, where biodegradability is important.

The catalyst system of the present invention comprises (1) nickel orpalladium complexed with certain fluoro-organothiol or sulfide ligandsand a reducing agent selected from the group of organic aluminumhalides- or alkoxides- and borohydrides.

The present process for preparing the catalyst of the invention,comprises contacting nickel or palladium or a salt thereof with afluoro-organothiol or sulfide followed by the addition of said organicaluminum halide or alkoxide or borohydride.

Broadly, the oligomerization process of the present invention comprisescontacting a C₂ -C₈ olefin (e.g., propylene, 2-hexene, 4-octene, etc.)with the present catalyst under reactive (oligomerization) conditions.

The invention will be further described herein below.

FURTHER DESCRIPTICN OF THE INVENTION AND PREFERRED EMBODIMENTS

The nickel or palladium complex portion of the present catalyst can bedescribed as a complex formed by a salt of nickel or palladium with anorganic ligand having at least one fluoro substituent and one --SRsubstituent wherein R is hydrogen or an optionally substitutedhydrocarbyl, for example, alkyl, alkenyl, alkynyl, aryl, alkylaryl,arylalkyl all of which can be optionally substituted with one or moresubstituents, such as, for example, independently selected from thegroup of halogen, oxygen, and hydrogen. Typically the fluoro-organothiolor sulfide is polysubstituted with respect to the fluoro substituents.As will be explained hereinbelow, the fluoro-organothiol or sulfide istypically monosubstituted with respect to the --SR substituent. Theligand should not contain any other ligating atom in a ligation positionwhich will displace fluorine as the ligand including a second sulfursubstituent. Such atoms or substituents are phosphorous, arsenic,selenium, tellurium or the coordinating forms of nitrogen (e.g., amines,cyclic amines, pyridines, heterocyclic amines) or as noted above, asecond sulfur atom. Preferably, the ligand should also not containchloro or bromo substituents in ligating positions though saidsubstituents are not as deleterious as the aforementioned atoms orsubstituents. The fluoro-organothiol or sulfide can contain such atomsor substituents provided they are positioned on the molecule such thatthey do ligate with the nickel or palladium moiety of the complex.

It is conjectured that in the present catalyst the fluoro substituent aswell as the sulfur substituent or moiety ligates with the nickel orpalladium atom, although technically, it may be more accurate to saythat a complex is formed because fluoro is such a weak ligand that itmay not be performing as a traditional chelating ligand in the complex.It is further conjectured that the fluoro moiety provides the linearselectivity in the present catalyst and that the stronger ligatinggroups reduce or destroy the linear selectivity by displacing the fluorosubstituent in the complex.

It has further been discovered that greatly superior results (e.g.,enhanced activity and selectivity) are obtained by using afluoro-organic sulfur compound wherein at least one of the fluorosubstituents is on a carbon atom adjacent the carbon atom containing thesulfur substituent. Examples of this structural part of thefluoro-organo sulfur compound can be represented by the followingpartial formulas: ##STR2##

Suitable fluoro-organic thiols which can be used include, for example,those having the formula (F)_(m) Z(SR) wherein Z is C₂ -C₈ alkyl; C₂ -C₈alkenyl; aryl having 6 to 10 carbon atoms; arylalkyl, having 6 to 10carbon atoms in the aryl substituent and 1 to 4 carbon atoms in thealkyl moiety; alkanoyl having 2 to 8 carbon atoms, alkanoylalkylenehaving 2 to 8 carbon atoms in the alkanoyl moiety and 1 to 6 carbonatoms in the alkylene moiety, or benzoyl; all of which can be optionallysubstituted with lower alkyl, lower haloalkyl, lower alkenyl, lowerhaloalkenyl, halo, C₁ -C₈ alkoxy nitro, or cyano. R is hydrogen orindependently selected from the same groups as set forth hereinabovewith respect to R¹ ; and m is an integer from 1 to 15, dependent uponthe size of the organic moiety Z and typically is 1-6.

Examples of ligands encompassed within the above formula include, forexample, pentafluorophenylthiol; 2-fluorothiophenol; 2-fluorcethylthiol;2-fluorothioacetaldehyde; 2-ethylthio-1-fluoroethylene;3-(4-fluorobutylthio)-4-fluoropent-1-ene; 2,3-difluorophenylthiol;2-fluoro-4-chlorobenzylthiol; 1-mercapto-2,3,4-trifluorobenzene;trifluorthioacetic-S-acid; pentafluorphenylmethyl mercaptan, and thelike.

Preferred fluoro-organic thiols and sulfides are those having theformula R₁ SR wherein R₁ is fluoroalkyl having 1 to 20 fluoro atoms and2 to 8 carbon atoms; fluoroaryl having 1 to 7 fluoro atoms and 6 to 10carbon atoms; fluoroarylalkyl having 1 to 5 fluoro-ring substituents and1 to 4 carbon atoms in the alkyl moiety; fluoroalkanoyl having 1 through13 fluoro substituents and 2 to 6 carbon atoms; fluoroalkanoylalkylenehaving 1 through 13 fluoro substituents and 2 to 6 carbon atoms in thealkanoyl moiety and 1 to 4 carbon atoms in the alkylene moiety andwherein said fluoro substituents can be on either the alkanoyl oralkylene moiety or both; aryl having 6 to 10 carbon atoms or arylalkylhaving 6 to 10 carbon atoms in the aryl moiety and 1 to 4 carbon atomsin the alkyl moiety optionally substituted with 1 to 4 fluoro groups andwith the proviso that a carbon atom adjacent the carbon atom containingthe sulfur substituent is substituted with at least one fluoro group andR is hydrogen, C₁ -C₈ alkyl; C₂ -C₈ alkenyl, aryl having 6 to 10 carbonatoms or arylalkyl, having 6 to 10 carbon atoms in aryl moiety and 1 to4 carbon atoms in the alkyl moiety; alkanoyl having 2 to 8 carbon atoms;alkanoylalkylene having 2 to 8 carbon atoms in the alkanoyl moiety and 1to 4 carbon atoms in the alkylene moiety; substituted groups selectedfrom the same groups as set forth hereinabove with respect to Rsubstituted with from 1 to 6 substituents indpendently selected from thegroup of lower alkyl, lower haloalkyl having 1 to 4 halo substituents,halo, lower haloalkenyl, or lower alkoxy.

Typically, best results have been obtained using pentafluorophenylthiol;methyl pentafluorophenyl mercaptan and ortho-fluorobenzenethiol. It isalso noted that unlike the catalyst complexes described in U.S. Pat. No.3,592,870 in which complexing likes place with respect to the ammonia oramine moiety and sulfur moiety, in the present case the complex isformed with respect to the sulfur moiety and probably the fluoridemoiety. Hence, the ligands used in the present catalyst do not requirean ammonium or amine substituent or component and as already discussedabove, such substituents or other substituents chelating with nickel orpalladium in preference to fluorine would be deleterious to the presentcatalyst.

The nickel and palladium complexes can be prepared by contacting theappropriate fluoro-organic thiol or sulfide complexing agent with nickelor palladium or a suitable salt thereof. Because of solubilityconsiderations, it is preferred to use a nickel salt or palladium saltrather than the elemental metal. This treatment is typically conductedat temperatures in the range of about from -10° to 180° C., preferably25° to 60° C. for about from 0 to 2 hours, preferably from 0 to 1/2 hourusing about from 1 to 5 moles, preferably 1 to 2 moles of complexingagent per mole of nickel or palladium. The treatment is typicallyconducted in an organic medium, such as, for example, chlorobenzene,methylene chloride, olefin and the like, and optionally in the presenceof a solubilizing agent which converts nickel or palladium in situ intoa soluble salt. Suitable salts which can be used include, for example,chlorides, bromides, iodides, sulfates, nitrates and carboxylates ofnickel or palladium, and the like. The carboxylate salts described inU.S. Pat. No. 4,366,087 can also be used.

The organoaluminum halide or organoaluminum alkoxide or borohydridereducing agent can then be admixed with the fluorothionickel orfluorothiopalladium complex. The organoaluminum halides and alkoxidesinclude, for example, those represented by the formula R*_(m) AlX_(n)wherein R* is C₁ -C₈ alkyl, aryl having 6 to 10 carbon atoms orarylalkyl having 6 to 10 carbon atoms in the aryl moiety and 1 to 4carbon atoms in the alkyl moiety; X is fluoride, chloride, bromideiodide or C₁ -C₈ alkoxide and m is 1 or 2 and n is 3-m. Suitable,organic aluminum halides and alkoxides which can be used include, forexample, alkyl aluminum halide (e.g., dimethyl aluminum chloride, ethylaluminum sesquichloride; dipropyl aluminum bromide; dibutyl aluminumiodide; methyl aluminum sesqui fluoride; aryl and arylalkyl aluminumhalides (e.g., phenyl; aluminum sesquiiodide; dibenzyl aluminumchloride; alkyl aluminum alkoxides (e.g., diethyl aluminum ethoxide);ethyl aluminum diethoxide; aryl and arylalkyl aluminum alkoxides (e.g.,phenyl aluminum diethoxide; dibenzyl aluminum t-butoxide); and the like.

Typically, the organoaluminum halide or alkoxide or borohydride is addedto fluorothionickel or fluorothiopalladium complex at temperatures inthe range of about from 0° to 150° C., preferably, 20° to 90° C. usingabout from 1 to 7 moles of organic aluminum halide or alkoxide.

Where the oligomerization is conducted as a batch process, the catalystcan be conveniently prepared in situ in the reactor followed by theaddition of the olefin feed stock. The oligomerization can also beconducted as a continuous, semi-batch or multi-step process. Theoligomerization can be conducted using suitable equipment and processdetail such as are, for example, conventionally employed in this art.Typically, the oligomerization is conducted as a liquid phase reactionby contacting the olefin feedstock, which can be a single olefin or, asis frequently the case, a mixture of olefins, with the present catalystat temperatures in the range of about from 0° to 120° C., preferably 50°to 90° C. using a feedstock to catalyst ratio of about from 0.00001 to0.01, of catalyst per mole of olefin feed. The polymerization isgenerally conducted at pressures in the range of about from 1 to 45atmospheres, and preferably at least sufficient to maintain a liquidphase system.

The present process and catalyst is especially useful for theoligomerization of propylene feedstocks to produce high yield of C₆ -C₃₀olefin oligomers having a high proportion of linear oligomers. Theproduct oligomers can be isolated from the reaction product mixture byany suitable procedures, for example, distillation, extraction, and thelike. If higher molecular weight polymers are desired, the linearolefins can be separated and the oligomerization repeated. Unreactedfeedstock and lower molecular weight olefins can be recycled back to theinitial feedstock. Where linear products are desired, substantiallylinear olefins (i.e., having a linearity of at least about 80% byweight), should also be used as the feedstock.

It should also be appreciated that where typical or preferred processconditions (e.g., reaction temperatures, times, mole ratios ofreactants, catalyst ratio, type of solvents, etc.) have been given, thatother process conditions could also be used. Optimum reaction conditions(e.g., temperature, reaction time, reactant ratios, catalyst ratios,solvents, etc.) may vary with the particular reagents or organicsolvents used but can be determined by routine optimization procedures.

Definitions

As used herein, the following terms have the following meanings unlessexpressly stated to the contrary:

The term "lower alkyl" refers to both straight-and branched-chain alkylgroups having a total of from 1 through 6 carbon atoms, preferably 1through 4 carbon atoms and includes primary, secondary and tertiaryalkyl groups. Typical lower alkyls include, for example, methyl, ethyl,n-propyl, isopropyl, n-butyl, t-butyl.

The term "lower alkene" or "lower olefin" refers to bothstraight-chained and branched-chained olefins groups having 2 through 8carbon atoms, preferably 2 through 4 carbon atoms. In the presentprocess the olefin feedstocks are preferably highly linear (i.e.,straight-chained).

The term "lower alkoxy" refers to the group --OR' wherein R' is loweralkyl.

The term "alkanoyl" refers to the group having the formula: ##STR3##wherein R' is alkyl having 1 to 7 carbon atoms, preferably 1 to 5 carbonatoms. Typical alkanoyl groups include, for example, acetyl, propionyl,CH₃ CH(CH₃)C(O)--; CH₃ (CH₂)₆ C(O)-- and the like.

The terms "alkanoylalkyl"; alkanoylalkylene" and alkanoylalkylidene"refer to the group ##STR4## wherein R' is as defined with respectalkanoyl and R" is alkylene having 1 to 6 carbon atoms, preferably 1 to4 carbon atoms, and can be straight- or branched-chained. Typical"alkanoylalkyl" groups include, for example, --CH₂ C(O)CH₃ ;--CH(CH₃)C(O)C₂ H₅,--CH₂ CH₂ C(O)CH₂ CH(CH₃)₂ and the like.

The term "halo" refers to the group of fluoro, chloro, bromo and iodo.

The term "aryl" refers to aryl groups having 6 through 10 carbon atomsand includes, for example, phenyl, naphthyl, indenyl. Typically the arylgroup will be phenyl or naphthyl as compounds having such groups aremore readily available commercially than other aryl compounds.

The term "arylalkylene" or "arylalkyl" refers to the group ArR³ --wherein Ar is aryl and R³ is alkylene having 1 through 3 carbon atomsand includes both straight-chained and branched-chained alkylenes, forexample, methylene, ethyl, 1-methylethyl, and propyl.

The term "(substituted aryl)alkylene" or "substituted arylalkyl" refersto the group Ar'R³ - wherein Ar' is substituted aryl and R³ is alkyleneas defined with respect to arylalkylene.

A further understanding of the invention can be had from the followingnon-limiting examples.

EXAMPLES EXAMPLE 1 Preparation of Nickel Bis(Fluorothiolate)

3.4 Grams of pentafluorothiophenol dissolved in 15 ml of acetone wereadded dropwise to a filtered solution of 1.83 gr of nickel acetate 4H₂ Oin 50 mls of 1:1 acetone/water. The slow addition of 150 mls of watercaused the precipitation of brown nickel bis(pentafluorophenylthiolate).Filtration and drying in a vacuum oven gave 2.9 gr of bis-thiolate.

Palladium bis(pentafluorophenylthiolate) can be prepared by applying theabove procedure using palladium acetate in place of nickel acetate.

EXAMPLE 2 Oligomerization of Propylene-Nickel Catalyst Complex

229 Mgs of nickel bis(pentafluorophenylthiolate) was slurried in 5 gr ofchlorobenzene and was transferred to a stirrer bomb and sealed. 480 Mgsof 25 wt. % solution of diethyl aluminum chloride in heptane was addedto 5 gr of chlorobenzene and transferred to a hoke bomb. The hoke bombwas pressured with 110 psi of propylene and attached to the stirrerbomb. After flushing the stirrer bomb two times with propylene, thediethyl aluminum chloride solution was blown into the reactor at 60° C.and the propylene pressure in the reactor adjusted to 130 psi. After 20hours, 6.23 gr of products were obtained with the distribution shown inTable 1 hereinbelow.

EXAMPLE 3 Oligomerization of Propylene-Palladium Catalyst Complex

252 Mgs of palladium bis(pentafluorophenylthiolate) and 5.83 gr ofchloro benzene are reacted with 520 mgs of 25 wt. % diethyl aluminumchloride in toluene under propylene pressure as in Example 2. 9.22 Gr ofproducts were obtained from the reaction whose distribution is shown inTable 1 hereinbelow.

EXAMPLE 4 Oligomerization of Propylene

22 Mgs of potassium t-butoxide were slurried together with 40 mgs ofpentafluorothiophenol in 5.5 grams of chlorobenzene. 62 Mgs of nickel2-ethylhexanoate trifluoroacetate were added after several minutes.After further stirring, 312 mgs of 25 wt. % ethyl aluminum chloride intoluene are added and the red solution is sealed into a bomb along with5 grams of propylene. The reaction is continued at 75° C. for 4 hours,then analyzed by gas chromatography. 1.9 Grams of oligomers wereobtained whose distribution is shown in Table 1.

EXAMPLE 5 Comparison Oligomerization of Propylene

62 Mgs of nickel 2-ethylhexanoate trifluoroacetate (referred to in U.S.Pat. No. 4,366,087 as nickel 2-ethyl hexanoate trifluoroacetate) in 2grams of heptane were reacted with 180 mgs of diethyl aluminum chlorideunder propylene pressure as in Example 2 at 42° C. for 2 hours. 140Grams of products were obtained whose distribution is shown in Table 1.Only a minor fraction of each oligomer is linear olefins.

The products obtained in Examples 2-5 were analyzed for olefindistribution and linearity (straight chain olefins).

The olefin distribution and percent linearity of each olefin fractin ofthe products of Examples 2-5 are summarized in Table 1 hereinbelowwherein percentages refer to weight percents.

                                      TABLE 1    __________________________________________________________________________    Example 2      Example 3 Example 4 Example 5    Olefins         Weight %               L* %                   Weight %                         L* %                             Weight %                                   L* %                                       Weight %                                             L* %    __________________________________________________________________________    C.sub.6 =         42.2% 80% 46.2% 74% 48%   79% 85%   23%    C.sub.9 =         30.2% 69% 33.5% 57% 30%   56% 14%    5%    C.sub.12 =         11.5% 49% 13.3% 28% 12%   47%  1%   --    C.sub.15 =          4.5% 37%  4.8% 19%  4%   --  --    --    C.sub.18 =         2%    35%  1.4% 19%  2%   --  --    --    C.sub.21 =+         9%    --  1%    --   4%   --  --    --    __________________________________________________________________________     *L = Linearity

As can be seen from the above Table, Examples 2-4 using the presentinvention afforded oligomer products having a high degree of linearity,whereas Example 5 using the same nickel salt catalyst complex, butlacking the fluoroorganic thiolate complexing agent, produced a producthaving poor linearity and also having a substantially different olefindistribution.

EXAMPLE 6 Oligomerization of Hexene

31 Mg of nickel 2-ethylhexanoate trifluoroacetate were dissolved in 4grams of n-hexenes and 36 mg of diethyl aluminum chloride were added tothis solution. The reaction was stirred at 65° C. for 5 hours. Analiquot was removed for g.c. analysis. This indicated that 0.23 gr ofhexene had been converted to oligomers with 97% selectivity tododecenes. Hydrogenation of these olefins indicates that the dodecenesconsist of 79% mono- and unbranched structures, and 21% doubly brancheddodecenes.

EXAMPLE 7 Oligomerization of Hexene

46 Mg of nickel bis(pentafluorophenylthiolate) were added to 4 gr ofn-hexenes and 36 mgs of diethyl aluminum chloride. The reaction andanalysis were run identically to Example 6. 0.7 Gr of hexenes had beenconverted to oligomers consisting of 94% dodecenes. Hydrogenation ofthese olefins indicates that the dodecenes consist entirely of mono- andunbranched structures.

Obviously, many modifications and variations of the invention describedhereinabove and below can be made without departing from the essence andscope thereof.

What is claimed is:
 1. A process for oligomerizing a lower olefin having2 to 8 carbon atoms which comprises contacting said lower olefin with acatalyst composition under oligomerization conditions at temperatures inthe range of about from 0° to 100° C. and pressures in the range ofabout from 1 to 45 atmoshperes and wherein said catalyst compositioncomprises a transition metal complex selected from complexes of nickeland palladium with a fluoro-organic thiol or sulfide ligand, having asingle sulfur atom in a ligating position and wherein the carbon atomadjacent the carbon to which the sulfur atom is attached has at leastone fluoro substituent and with the proviso that said fluoro-organicthiol or sulfide does not contain any other ligating group or atom in aligating position which will displace fluoro as a ligand, and anorganometallic-reducing agent selected from the group of borohydride andorganoaluminum halides and alkoxides having the formula R*_(m) AlX_(n)wherein R* is alkyl, aryl or arylalkyl; X is fluoride chloride, bromide,iodide or alkoxide and m is 1 or 2 and n is 3-m.
 2. The process of claim1 wherein said olefin is a mixture of substantially linear olefins. 3.The process of claim 2 wherein said olefin is propylene.
 4. The processof claim 1 wherein the reducing agent in said catalyst composition isselected from the group of borohydride; diethylaluminum ethoxide;ethylaluminum sesquichloride; and said fluoro-organic thio or sulfide isselected from the group of pentafluorophenylthiol; methylpentafluorophenyl mercaptan; and ortho-fluorobenzenethiol.
 5. Theprocess of claim 4 wherein said olefin is a mixture of substantiallylinear olefins.
 6. The process of claim 5 wherein said olefin ispropylene.
 7. The process of claim 1 wherein said transition metalcomplex is a nickel complex.
 8. The process of claim 1 wherein saidtransition metal complex is nickel complex with a ligand ofpentafluorophenylthiol; (loweralkyl)thio-pentafluorobenzyl; ortrifluorothioacetic-S-acid.